1. Technical Field
The present invention relates to a writing device, a display sheet, and an electronic device.
2. Related Art
An electrophoretic display sheet using electrophoresis of particles is known as a constituent component of a display unit (image display unit) of electronic paper, for example. Moreover, as an input device for displaying a desired image on such an electrophoretic display sheet, a pen type input device used in a state gripped by a user like a writing material, such as a pencil or a ball-point pen, is known (for example, refer to JP-A-2007-206846).
An information input device disclosed in JP-A-2007-206846 includes a main body in which an electrophoretic display sheet (electronic paper) is placed, a pressing section which presses the electronic paper placed in the main body from above, and a pen type position indicator (input device). In this information input device, a matrix electrode portion (a plurality of dot electrodes) provided so as to be in contact with the electronic paper is formed in the main body, and a transparent electrode is formed in the pressing section.
Moreover, in the information input device disclosed in JP-A-2007-206846, when a user holds the pen type position indicator and draws a desired locus on the pressing section with the electronic paper interposed therebetween (that is, in a state where a transparent electrode and matrix electrodes face each other with the electronic paper interposed therebetween), a controller provided in the main body detects the locus (that is, coordinates of the pen type position indicator) on the basis of a predetermined signal transmitted from the pen type position indicator, selects dot electrodes corresponding to the locus from the matrix electrode portion (a plurality of dot electrodes), and applies a voltage between the selected dot electrodes and the transparent electrode. Then, a display color of a portion, which corresponds to the locus, on the display surface of the electronic paper changes, and an image corresponding to the locus is displayed on the display surface of the electronic paper accordingly.
In such an information input device, the pen type position indicator is not wired with the main body through a conductive wire (that is, the pen type position indicator is wireless). Accordingly, since the conductive wire or the like is entangled with neither the pen type position indicator nor a hand when moving the pen type position indicator on the pressing section, the information input device is easy to use (is excellent in terms of convenience).
In such an information input device, however, in order to realize the wireless function and excellent convenience, it is necessary to provide a circuit (resonance circuit) for transmitting a predetermined signal in the pen type position indicator and also to provide a controller, which detects the coordinates of the pen type position indicator, in the main body. As a result, there is a problem in that the configuration becomes complicated.